This invention relates to driver-vehicle behavior display apparatus and more particularly to video display apparatus for relating a driver's actions to a vehicle's performance capabilities in real time superimposed upon the driver's view of the roadway ahead and the present steering wheel position.
The tire performance envelope, friction circle or g--g diagram concept as the same has been variously referred to, was developed by Calspan Corporation in the late '60's as a simple way of graphically demonstrating the performance of a given driver in a given vehicle during a single maneuver. While the concept of the tire performance envelope, friction circle or g--g diagram is best explained in the paper entitled "Measuring Car-Driver Interaction With The g--g Diagram," by R. S. Rice, Vehicle Reseach Dept., Calspan Corporation, as published at the International Automotive Engineering Congress conducted in Detroit, Mich. on Jan. 8-12, 1973 as Paper 730018 by the Society of Automotive Engineers, the same is based upon a recognition that the forces available to a driver in controlling a vehicle are derived at the tire-roadway interface. Therefore, by proper application of the brake, throttle, and steering device, and only through these devices, the driver of a vehicle can utilize the forces which are developed at the tire-roadway interface (contact patch) to produce vehicle motions in performing specific maneuvers. The fundamental constraint upon the system is, however, found in the tire-road coefficient of friction at the tire contact patch and hence regardless of a driver's ability, unlimited capability is not present for the taking. Thus, the tire-roadway performance parameter represents a maximum boundary on the g--g diagram which, when surpassed, results in a loss of control.
The tire performance envelope, friction circle or g--g diagram concept simply assumes that the maximum force that can be generated by the tire is independent of direction and that the magnitude is equal to the normal force times the sliding friction coefficient. While not strictly true, assuming that a tire has relatively equal traction capabilities in any direction, i.e. acceleration, braking, or cornering in either a right or left direction, results in a plot in the form of a circle or ellipse which depicts the outer limit of a vehicle's capability. If these are exceeded, a loss of control results. Thus, such a circle may be characterized as a performance envelope corresponding to the capabilities of a vehicle. In typical cases this performance envelope for street vehicles will have a radius which corresponds to the vector acceleration magnitude in g units corresponding to 0.7 g's.
If this performance envelope is plotted symmetrically on an X and Y axis, g force due to left cornering may be indicated from the zero location where the ordinate and abscissa intersect along the abscissa in a positive direction. G forces associated with right cornering may be indicated from the zero location along the abscissa in the left direction. Conversely, braking force may be indicated along the ordinate from the zero location in the upward direction while g forces due to acceleration may be located along the ordinate from the zero location in a negative direction.
The g forces imposed on a vehicle by a driver's action in applying the brake, throttle and steering wheel in performing a given maneuver may then be plotted on the same axis to provide a direct comparison of the manner in which the driver utilizes the vehicle's capabilities in performing the maneuver. Examples of how this may be done and uses therefor are set forth within the article entitled "What's It Really Like Out There?" by Paul Van Valkenberg as published in Road and Track Magazine, Oct. 1983, pages 67-69. Application of the g--g diagram to training race drivers is also described in the article entitled "How To Go Faster" by Bert Levy, published in Sports Car Magazine, October 1985 at pages 70-73.
While the concept of the g--g diagram or friction circle concept is extremely useful in training race car drivers and for assisting engineers in evaluating performance characteristics of various vehicles, its uses to data have been highly limited and frequently difficult since in each case the vehicle under test must be equipped with a computer capable of monitoring g force accelerometers for braking, acceleration and left and right cornering. Typically a strip chart recorder is employed to print out the g forces monitored as a result of a specific maneuver or those which occur as a result of a series of maneuvers. The resulting strip chart then must be interpreted by a skilled technician in terms of the actual maneuver performed and the events recorded analyzed in light of the precise events which occurred during the course of that maneuver as well as the performance envelope of the vehicle. This is not only difficult but often presents the data to a user in such a manner that correlation to real time and to the maneuver being conducted is so onerous as to preclude full utilization and understanding of the data obtained.
Therefore, it is a principal object of the present invention to provide improved driver-vehicle behavior display apparatus.
A further object of the present invention is to provide video g--g diagram display apparatus presenting driver's actions in real time in terms of a polar plot of g force imposed by a driver on a vehicle superimposed upon a vehicle performance envelope.
Another object of the present invention is to provide video g--g diagram display apparatus for relating a driver's actions to a vehicle's performance capabilities on a real time basis superimposed upon a driver's view of the roadway being traversed.
Another object of the present invention is to provide video g--g diagram display apparatus for relating driver's actions to vehicle performance capabilities on a real time basis superimposed upon a driver's view of the roadway and the steering wheel position.
A further object of the present invention is to provide video g--g diagram display apparatus for relating a driver's action to a vehicle's performance capabilities on a real time basis superimposed upon a driver's view of the roadway being traversed and a bar graph indicating throttle and brake engagment.
Various other objects and advantages of the present invention will become clear from the following detailed description of an exemplary embodiment thereof and the novel features will be particularly pointed out in conjunction with the claims appended hereto.